The aims of this project are (a) to gain better understanding of the abnormalities of control of breathing in patients with chronic obstructive lung disease (COLD); (b) to reassess the limitations of the conventional techniques used for studying lung volumes and mechanics (body plethysmography and measurement of esophageal pressure); and (c) to determine the threshold for development of inspiratory muscular fatigue in stable COLD patients during the performance of different natural activities. Probably for the first time, the control of breathing in COLD patients will be studied using in parallel the most up-to-date techniques, namely electromyography, spectral analysis of electromyograms, magnetometry, lung mechanics measurements, ventilation, breathing pattern, mouth occlusion pressure, analysis of shape of spirogram and pneumatachogram, etc. In a sense this investigation represent the fruition of long years of research which has led to the development of various techniques for the study of different aspects of respiratory function. These techniques will be here combined and reassessed, in order to obtain a more coherent picture of the abnormalities of control of breathing in COLD. Such new information is needed in order to develop optimal care for COLD patients.